Technique and radiation

• Contraindicated in pregnant patients and those with a history of intravenous contrast allergy

• Fluid restriction is not required with modern low osmotic media

• Bowel preparation while desirable, is not mandatory

• Control KUB film is taken to identify any areas of calcification which may be obscured later by contrast

• 50 mL to 100 mL of contrast medium (1 mL/kg body weight of 300 mg of iodine per mL of solution) is injected into the antecubital vein using an 18-gauge cannula

Sequence of films post-contrast injection (all films AP view):

• Immediate film: within 1 minute of injection (arm to kidney time is approx 15 seconds). This demonstrates the nephrogram

FIGURE 3.2. IVU showing partially obstructing right upper ureteric calculus at (a) 15 and (b) 30 minutes following contrast; (c) complete obstruction due to left proximal ureteric stone and (d) tomogram showing TCC renal pelvis and lower pole infundibulum and calyces (Courtesy of Dr A Bradley, Wythenshawe, Manchester)

FIGURE 3.2. IVU showing partially obstructing right upper ureteric calculus at (a) 15 and (b) 30 minutes following contrast; (c) complete obstruction due to left proximal ureteric stone and (d) tomogram showing TCC renal pelvis and lower pole infundibulum and calyces (Courtesy of Dr A Bradley, Wythenshawe, Manchester)

(contrast in the renal tubules) which will be dense in the presence of obstruction. After a delay of 2-3 min, contrast enters the collecting system and reveals the pyelogram. Some radiologists recommend up to three tomographic views during the immediate phase at the level of a third of the AP diameter of the patient (—8—12 cm) to provide easier identification of renal calcification and masses. Tomography is not routinely used now. If such details are needed CT is usually preferred

• 5-min film: this demonstrates the full pyelographic phase with visualization of the collecting system and the proximal (and sometimes distal) ureter. The sequence of further films is determined by this film. Note any dilatation (suggestive of obstruction/stasis) and filling defect (peristalsis, tumors, stones). A compression band applied at the level of the anterior superior iliac spines (corresponding to the ureters crossing over the pelvic brim) will produce better pelvicalyceal filling. Avoid compression if—

i. Abdominal trauma ii. After recent renal surgery iii. In the presence of a large abdominal mass iv. In demonstrable upper tract obstruction

• 15-min film: may be performed to show the lower ureter

• Release film: may be performed after release of compression to visualize the whole urinary tract

• Post-micturition film: allows assessment of bladder emptying, but is also useful in diagnosing bladder tumors, juxtavesical stones, and urethral diverticulum. Also note if any relief of presumed upper tract dilatation following micturition

• Delayed films: may be useful at intervals of 1, 4, 12, and 24 hours following contrast injection if obstructed

• Other films: oblique views may help clarify location of calcification. Prone films provide better ureteric filling. Erect films are best for showing renal ptosis and cystoceles

Effective radiation dose is 4.6 mSv (equivalent to 2.5 years of background radiation or 11,500 miles traveled by car).

NB: For an on-table IVU, larger doses of contrast (up to 200 mL) are frequently required. A combination of poor intra-operative renal perfusion and inadequate bowel preparation usually results in poor images. Most commonly a single film is taken 10 minutes following the contrast injection, but a sequence of films can be performed at 1, 5, 15, and 30 minutes.

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